The present invention relates to a process for preventing the pumping of a hydraulic valve clearance compensating element in a valve operating mechanism of an internal combustion engine, wherein a valve actuating lever is supported by means of a hydraulic valve clearance compensating element and is controlled by a cam and to a valve operating mechanism for conducting this process.
In valve operating mechanisms of internal combustion engines, the positive connection between the valve actuating lever and the cam shaft is frequently lost, especially at high speeds, so that the so-called "valve soaring" occurs. When using hydraulic valve clearance compensating elements, this leads to the so-called "pumping" thereof, due to their resetting function, so that the valves can no longer close entirely.
An object of the present invention is to provide a process for preventing the pumping of the hydraulic valve clearance elements in internal combustion engines with a valve operating mechanism of the aforementioned type of construction, as well as a valve operating mechanism for conducting this process.
This object has been attained according to the present invention in that in the process of the present invention during the valve lifting phase of the cam an auxiliary force is applied to the valve clearance compensating element, counteracting the compensating force of this valve clearance element, this force being greater than the compensating force and being independent of the bearing force of the valve actuating lever. The valve operating mechanism of the present invention for conducting this process includes a structural arrangement which is responsive to the movement of the cam for applying an auxiliary force to the valve clearance compensating element, the auxiliary force during the valve lifting phase of the cam being greater than and directed to counteract the compensating force of the valve clearance compensating element.
According to a disclosed embodiment of the present invention the valve operating mechanism includes a rod which is supported at one end and which resiliently contacts the valve actuating lever at its other end, the rod contacting the valve actuating lever in a bearing zone of the lever and on a side of the lever in opposition to the valve clearance compensating element. A section of the rod is positioned with respect to the cam so as to respond to the movement of the cam during the valve lifting phase thereof whereby the auxiliary force is applied to the compensating element.
In this disclosed embodiment the rod is resilient and is mounted so as to be pretensioned when resiliently contacting the lever, the tension in the rod being increased in response to the movement of the cam during the valve lifting phase thereof. The movement of the cam during this valve lifting phase is transmitted to the rod via the valve actuating lever in that the valve actuating lever contacts the cam with a sliding surface on the lever and the rod in turn contacts an abutment surface formed on the lever in close proximity of the sliding surface and in opposition thereto.
According to the disclosed embodiment of the valve operating mechanism the rod has a bifurcate section at one end and contacts, with the legs of the bifurcate section, the abutment surface which is arranged on both sides of the lever.
It is possible by means of the process of this invention in conjunction with the valve operating mechanism of the invention to effectively prevent the pumping of the valve clearance compensating element and maintain the function of this element during the base circle phase of the cam, so that valve clearance compensation is ensured.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment in accordance with the present invention .